Pension and Other Postretirement Benefit Plans - Obligation and Funded Status (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in Plan Assets [Roll Forward]
Non-Current Liabilities		$ (206.8)	$ (190.9)
Other Investments		74.6	114.4
Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation		665.0	661.4
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year		714.5	622.8
Service Cost		10.1	8.3	$ 9.9
Interest Cost		29.9	29.8	26.0
Actuarial (Gain) Loss		(31.2)	72.6
Benefits Paid		(40.2)	(36.9)
Participant Contributions		26.7	17.9
Obligation, End of Year		709.8	714.5	622.8
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year		544.2	501.6
Actual Return on Plan Assets		(10.8)	41.0
Employer Contribution	[1]	28.1	38.5
Benefits Paid		(40.2)	(36.9)
Fair Value, End of Year		521.3	544.2	501.6
Funded Status, End of Year		(188.5)	(170.3)
Current Liabilities		(1.3)	(1.2)
Non-Current Liabilities		(187.2)	(169.1)
Postretirement Health and Life [Member]
Change in Benefit Obligation [Roll Forward]
Obligation, Beginning of Year		170.9	151.9
Service Cost		4.3	3.4	3.9
Interest Cost		7.2	7.3	6.8
Actuarial (Gain) Loss		(14.4)	18.1
Benefits Paid		(10.7)	(8.9)
Participant Contributions		2.9	2.6
Plan Amendments		0.0	(2.9)
Plan Curtailments		0.0	(0.6)
Obligation, End of Year		160.2	170.9	151.9
Change in Plan Assets [Roll Forward]
Fair Value, Beginning of Year		163.2	157.0
Actual Return on Plan Assets		(3.5)	11.6
Employer Contribution		1.5	1.1
Participant Contributions		2.9	2.6
Benefits Paid		(10.7)	(9.1)
Fair Value, End of Year		153.4	163.2	$ 157.0
Funded Status, End of Year		(6.8)	(7.7)
Non-Current Assets		6.4	6.6
Current Liabilities		(1.0)	(0.9)
Non-Current Liabilities		(12.2)	(13.4)
Irrevocable Grantor Trust [Member]
Change in Plan Assets [Roll Forward]
Other Investments		$ 17.4	$ 17.9

[1] Includes Participant Contributions noted above.